In his final plea to have charges dropped against WikiLeaks suspect Bradley Manning, a defense lawyer Tuesday compared his harsh detention conditions to those of a "zoo animal."

Manning's solitary confinement -- under 24-hour watch, forced to sleep naked in a tiny cell for all but 20 minutes a day -- was "a clear violation" of the US code of military justice, defense lawyer David Coombs said.

"There was this eight-by-six (foot) cell, that was PFC (Private First Class) Manning's life," Coombs said, as both the defense and the prosecution wrapped up arguments to close off a dramatic phase of pre-trial hearings.

"Every moment of your life is going to be subjected to being watched... watched or viewed almost as a zoo animal," Coombs said.

The 24-year-old private faces a slew of charges, including "aiding the enemy," for allegedly leaking hundreds of thousands of sensitive US military and diplomatic documents to Julian Assange's anti-secrecy site WikiLeaks.

He was arrested in May 2010 while serving as an intelligence analyst near Baghdad and subsequently charged over the largest leak of restricted documents in history.

Manning was sent briefly to a US jail in neighboring Kuwait, before being transferred to Marine Corps brig in Quantico, Virginia in July 2010.

After nine months in the brig, he was moved in April 2011 to a US Army prison at Fort Leavenworth, Kansas, where he was allowed to interact with other detainees as detention conditions were relaxed.

During pre-trial hearings at Forte Meade in Maryland, the defense has focused on getting the charges dropped on the basis that Manning's detention conditions at Quantico were unfairly harsh.

"It was arbitrary, month after month," Coombs said. "If the conditions are not necessary that could give rise to illegal punishment," which would justify dropping all the charges, he said.

The court has heard from the full hierarchy of figures involved in Manning's incarceration -- from the prison chief to the guards that kept watch over his cell.

The suspect took the stand himself, admitting he had broken down early on his detention and contemplated suicide but adding that he had recovered only for his pleas for better conditions to fall upon deaf ears.

"I had no socks, no underwear, I had no articles of clothing, I had no glasses," testified Manning, who also complained bitterly about the uncomfortable suicide-prevention smock he was made to wear.

During about five hours of testimony, Manning showed flashes of humor as he calmly recounted the severe restrictions and monotony he faced during his pre-trial confinement in both Kuwait and Quantico.

The boyish-looking soldier recounted how he was forced to stand at attention naked in his cell and encountered angry responses when he questioned his detention regime.

A US military psychiatrist testified that the draconian "prevention of injury" status was "senseless" and that commanders had totally ignored his advice to lift tough suicide watch measures earlier.

But the court also heard how Manning fashioned a noose from a bedsheet in Kuwait and had written that he was considering suicide. Manning insisted he was always thinking such thoughts but never planned to act on them.

Prosecutors, broadly-speaking, defended the harsh detention conditions, although they did concede that Manning was improperly held on suicide watch for one week and should have that time struck off his sentence.

In conclusion, prosecutor Ashden Fein stressed that the removal of Manning's underwear, for example, complied with government regulations and had been done out of "a legitimate interest for safety and security.

"It was the only option or to put (Manning) back to suicide watch which is the most intrusive status," he added.

Army Colonel Denise Lind, the military judge presiding over the Manning case, has not said when she will rule.

Manning, who is six days shy of his 25th birthday, could spend the rest of his life in prison if he is convicted.

The next pre-trial hearing is set for January 8. The case is expected to go to full trial in March, unless the charges are dismissed, which is considered unlikely.